1. Field of the Invention
The present invention relates to a gain controlling unit configured to output a control signal to radio frequency signal attenuation circuitry and intermediate frequency processing circuitry.
2. Background of the Related Art
Mobile radio communications systems are used in everyday life. Garage door openers, remote controllers for home entertainment equipment, cordless telephones, hand held walkie-talkies, pagers, and cellular telephones are all examples of mobile radio communications systems. The term mobile has historically been used to classify any radio terminal that can be moved during operation. More recently, the term mobile is used to describe a radio terminal that is attached to a high speed mobile platform (e.g., a cellular phone in a fast moving vehicle) whereas the term portable means a radio terminal that can be hand-held and used by someone at a walking speed (e.g., a walkie-talkie or cordless telephone inside a home). The term subscriber is often used to describe a mobile or portable user because in most mobile communications systems, each user pays a subscription fee to use the system, and each user's communication device is called a subscriber unit. In general, the collective group of users in a wireless system are called users or mobiles, even though many of the users may actually use portable terminals. The mobiles communicate to fixed base stations which are connected to a commercial power source and a fixed backbone network.
Many radio terminals both transmit and receive radio frequency signals. Due to changes of location or other environmental changes, the power level of the signals transmitted and received from radio terminals can vary. This can become problematic in radio terminals when the strength of a received radio frequency signal is too high. When the strength of such a radio frequency signal is too high, the radio terminal may not be able to process the signal properly. In these instances, a received radio signal may appear or sound distorted to a user. Particularly, when a radio terminal receives a high power radio frequency (RF) signal, the components of the radio terminal may become saturated and cause the undesirable distortion. Another disadvantage of a radio terminal receiving a high voltage signal is that the radio terminal may become disconnected, which is annoying to the user.